Tobacco smoke filter element

ABSTRACT

A cigarette smoke filter for removing Polonium 210 contained in cigarette smoke, in which finely divided aluminum particles are uniformly dispersed in a carrier base of high surface area, the particles acting to absorb Polonium 210.

United States Patent [72] inventor Ernest Marsden Lowry Bay, Wellington,New Zealand [21] Appl. No. 658,351 [22] Filed Aug. 4, 1967 [45] PatentedJan. 26, 1971 [73] Assignee Larus & Brother Company Richmond, Va.

[54] TOBACCO SMOKE FILTER ELEMENT 50 Field of Search .l 131/10;131/261-269. 10.9, 207, (inquired); 55 74, 72

[56] References Cited UNITED STATES PATENTS 3,039,475 6/1962 Neukomm etal. 131 140 Primary ExaminerMelvin D. Rein Attorneys-A. Yates Dowell andA. Yates Dowel], Jr.

ABSTRACT: A cigarette smoke filter for removing Polonium 210 containedin cigarette smoke, in which finely divided alu minum particles areuniformly dispersed in a carrier base of high surface area, theparticles acting to absorb Polonium 210.

TOBACCO SMOKE FILTER ELEMENT The present invention relates to smokefilter elements suitable for in cigarettes or cigarette holders.

The object of the present invention is to provide a tobacco smoke filterelement which while performing the usual functions of such a filterregarding the removal of, for example tar, is also capable ofselectively absorbing the radioactive isotope Polonium 210 (Po2l0) fromtobacco smoke to a significant extent.

The basis of the present invention is the discovery that aluminum ishighly effective in adsorbing P0210 and that it may be incorporated intobacco smoke filter materials in a finely divided form to produce atobacco smoke filter element meeting the criteria set out above.

The invention consists in a tobacco smoke filter element forincorporation in a cigarette or cigarette holder the filter elementconsisting of a carrier base of high surface area in which particles offinely divided aluminum are substantially uniformly dispersed theaverage size of the particles being between 5 and 500 microns.

The disclosure describes in a method of making a tobacco smoke filterelement wherein a carrier base of high surface area filter material isimpregnated with a dispersion of aluminum particles in a liquid, theaverage size of the particles being in the range of from 5 to 500microns, the carrier base being formed into a rod of appropriatediameter before or after impregnation.

It is preferred that the carrier base shall be of fibrous material suchas cellulose acetate in fibrous form but it may also be of any othermaterial having a high surface area per unit weight suitable for use asa tobacco smoke filter element in which finely divided aluminumparticles may be dispersed.

It is further preferred that the aluminum particles be incorporated inthe carrier base by immersing the carrier base in a dispersion ofaluminum particles in a suitable liquid.

While it has been established that aluminum particles are capable ofselectively absorbing P0210, there is no experimental evidence to handas to whether a particular particle size range is most efficacious forP0210 adsorption, however, it is reasonable tolassume that since theadsorption is a surface area effect it would be inversely proportionalto the particle size. it is considered that aluminum particles in therange of from 5 to 500 microns may be used effectively for the purposesof the invention, particles in the size range of from 25 to 150 micronsbeing preferred.

The preferred carrier material is cellulose acetate fiber such as Estron(a registered trade mark of Eastman Chemical Co.) for two reasons (i)the filter-manufacturing technology is well established for such afiber, and (ii) cellulose acetate itself exhibits a slight selectivityfor P0210. However, it could be expected that aluminum would exhibit itsselectivity for P0210 irrespective of the carrier material by which itwas supported provided that material had a sufficiently high surfacearea and by virtue of this a sufficient number of spaces to occludesignificant quantities of aluminum particles.

The results set out below were obtained with plasticized Estrondesignated 3.5/44000 where the number 3.5 refers to the denier of thefilament (weight in grams of a single filament or fiber 9,000 meters inlength) and the 44000 refers to the total denier of the tow. The totalnumber of fibers in the tow is obtained by dividing the total denier bythe filament denier. It could be expected that the use of Estron ofanother denier, e.g. 8.0/70000 would produce a different selectivitywhen impregnated with aluminum particles by virtue of the reduced numberof fibers and consequently the number of interfiber spaces.

Although methods such as dusting and spraying may be used to incorporatethe aluminum particles in the fibrous carrier material, the method whichhas been found most effective for Estron is to immerse, for example, 7.5mm. X 7.8 mm. diameter plugs of plasticized Estron into a dispersion ofthe aluminum particles in a suitable liquid such as an organic solvente.g. n-Hexane. The aluminum particles dispersed in the solvent arerapidly incorporated throughout the plug by virtue of capillaryattraction. After drying in air or vacuum no trace of the solventremains, the plugs retaining only a uniform impregnation of aluminumparticles. The characteristics of a suitable liquid are:

i. a sufficiently low boiling point to expedite evaporation;

ii. freedom from noxious nonvolatile residues; and

iii. compatibility with the filter medium so as to cause no dimensionalchanges.

A particular advantage of this technique in contrast to the dusting andspraying techniques is that the filter is impregnated after plasticizingof the Estron fiber whereas the reverse procedure may significantlyreduce the surface activity of the aluminum particles. Other advantagesof this technique are its economy, simplicity, and suitability forcontinuous operation in contrast with, for example, thevacuumspluttering technique.

However, this liquid dispersion technique is only applicable to aluminumparticles whose diameters are smaller than the interfiber distances andwhen larger particles are being used, dusting and sieving of theparticles into the fibrous carrier material, or the use of a techniqueknown as the Eastman S|urry Additive Process, is necessary.

The weight of aluminum per unit volume of the filter can be altered bychanging the quantity of aluminum being dusted or sieved onto a movingband of fibrous carrier material such as Estron tow, or in the case ofthe liquid dispersion technique by the quantity of aluminum dispersedper unit volume of the bath.

For example, in the liquid dispersion technique, if the dispersion bathcontained l5 g. aluminum powder per liter, approximately 5 mg. aluminumwas deposited in a 7.5 mm. X 7.8 mm. diameter 3.5/44000 Estron plug; if30 g. per liter than approximately 10 mg. per plug; if 60 g. per literthen approximately 13 mg. per plug. The proportionally lower depositionat the highest dispersion concentration indicates saturation or anapproaching saturation for that denier Estron.

Test results are set out below in connection with one particular form offilter according to the invention the construction of which is describedby way of example only.

The test results set out below s were obtained from smoking tests ofcigarettes fitted with two 7.5 mm. X7 .8 mm. diameter 3.5/44000 Estronplugs in series. The Estron plugs were either plan plain or impregnatedwith aluminum particles of a total weight as stated. Smoking tests wereperformed according to the recommendations of the CORESTA ScientificCommission, Smoke Study Group, Jan. 1966. Eight groups of 10 cigaretteswere smoked for P0210 analysis and eight groups of five cigarettes weresmoked for tar and nicotine analysis. Both the cigarette filters and theCambridge filters were analyzed for the relevant smoke components.Filtration efficiencies were calculated according to the formula.

f F H where F= amount of smoke component retained on cigarette filterand H= amount of smoke component retained on Cambridge filter.

The total P0210 content of cigarettes smoked was of the order of 0.50 Ciper cigarette.

Filtration Efiiciency percent.

Filtration etficieney, percent Nicotine N0'1E.= Error terms are 1standard deviation limits.

The test results set out above are only examples of a typical degree ofselectivity obtained. Depending on the particular requirements e.g.whether increased tar filtration is required multiples or submultiplesof these filters may be used. Different results could be expected fromfilters made from Estron of a different denier or from filters ofdifferent lengths. It is estimated for example that a filter elementhaving a length of 22.5 mm. and containing about 38 mg. A1 would have afiltration efficiency for P02 l of about 66 percent.

It will be seen that the aluminum impregnated filter elements show asignificant improvement in their capacity to remove P0210 as comparedwith the unimpregnated filter elements.

A matter of some practical significance is that whereas the pressuredrop of an unimpregnated filter was l1.8 cms. of water this wasincreascd'only to I22 cms. of water in the case of the third impregnatedfilter containing about 26 mg. A1.

in the practical application of a tobacco smoke filter element accordingto the invention it is preferred that the filter element be followed bya length of plain unimpregnated filter material to prevent the possibleingestion of any loosely held aluminum particles.

lclaim: 1 y

l. A tobacco smoke filter element for incorporation in a cigarette orcigarette holder to remove Polonium 2l0, said filter element consistingof a carrier base of high surface area in which particles of finelydivided aluminum aresubstantially uniformly dispersed, the average sizeof the particles being between 5 and 500 microns.

2. A tobacco smoke filter element as claimed in claim I wherein thecarrier base is of fibrous material and the aluminum particles areretained in the interfiber spaces.

3. A tobacco smoke filter element as claimed in claim .2 wherein thefibrous material is cellulose acetate fiber.

4. A tobacco smoke filter as claimed in claim 3 wherein the average sizeof the aluminum particles is in the range of from 25 to microns.

1. A tobacco smoke filter element for incorporation in a cigarette orcigarette holder to remove Polonium 210, said filter element consistingof a carrier base of high surface area in which particles of finelydivided aluminum are substantially uniformly dispersed, the average sizeof the particles being between 5 and 500 microns.
 2. A tobacco smokefilter element as claimed in claim l wherein the carrier base is offibrous material and the aluminum particles are retained in theinterfiber spaces.
 3. A tobacco smoke filter element as claimed in claim2 wherein the fibrous material is cellulose acetate fiber.
 4. A tobaccosmoke filter as claimed in claim 3 wherein the average size of thealuminum particles is in the range of from 25 to 150 microns.